Field
Embodiments disclosed herein relate to a thread form for coupling and de-coupling threaded connections. More specifically, embodiments disclosed herein relate to a thread form that reduces stress and improves fatigue life of threaded connections that experience cyclical and/or vibrational loading.
Description of the Related Art
Threaded connections are widely used in the oil and gas industry to couple one or more devices together. These types of thread connections often experience significant vibrational forces and/or significant cyclical loading. One example includes high pressure reciprocating pumps, such as multiplex plunger pumps. These types of pumps have a fluid end that includes valves, plungers, liners, among other components, that is driven by a power end that converts the rotation of a drive shaft to the reciprocating motion of a plunger in the fluid end. These types of pumps can pump fluids into a wellbore at rates of up to 10 barrels per minute and at pressures up to 20,000 pounds per square inch (psi).
A fluid end typically includes three or more plunger bores. Each plunger bore houses a reciprocating plunger. The reciprocating plunger is coupled to the fluid end by a packing nut that includes male threads that interface with female threads of the fluid end. Typically, the male/female threads are of the same type or style. The thread interface of the male/female threads experiences shear forces in a cyclic manner when the fluid end is in operation. In particular, the threads are stressed along a shear plane that is substantially parallel to the longitudinal axis of the threads during operation of the fluid end, which causes fatigue and ultimately failure of the threaded interface. Additionally or alternatively, the threaded interface may experience vibrational forces which may cause loosening as well as premature failure of the connection.
Therefore, there exists a need for a new and improved threaded interface that prevents the failure described above.